Decreased periparturient transmission of bovine leukosis virus in colostrum-fed calves

BACKGROUND: The relation between calf bovine leukosis virus (BLV) infection status and colostrum ingestion is unclear. Two conclusions have been drawn from previous studies. One suggests that colostrum ingestion transmits BLV to neonatal calves. The second suggests that colostral antibodies are protective. HYPOTHESIS: Colostrum from BLV-positive cattle is protective in naturally exposed calves. ANIMALS: Twelve colostrum-deprived Holstein calves and 20 colostrum-fed Holstein calves born to BLV-infected cows. METHODS: Prospective study. Colostrum-deprived calves were tested weekly by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) tests for BLV antibody and provirus for 12 weeks or until the animal became positive for BLV infection. Colostrum-fed calves were fed colostrum derived from BLV-positive cows. Thereafter, ELISA and PCR tests for BLV antibody and provirus were performed every other week until 2 consecutive negative ELISA tests or 1 positive PCR test was achieved. The proportion of calves that converted to BLV-positive status was calculated for each group and compared between groups by using the Fisher exact test. RESULTS: Four of 12 colostrum-deprived calves (33%) became BLV positive, whereas 0 of 20 colostrum-fed calves (0%) became BLV positive. The proportion of calves that became infected was significantly higher in the colostrum-deprived group (P = .014). CONCLUSIONS AND CLINICAL RELEVANCE: Calves born to BLV-positive cows are exposed during parturition, and a proportion of these calves will become infected with BLV. Administration of colostrum from BLV-positive cows greatly decreases the risk of infection.     

Decay of colostral antibodies to bovine leukemia virus with application to detection of calfhood infection

An estimated weighted-regression method was used to describe the decay of colostral bovine leukemia virus (BLV) antibodies in the calf, as measured by agar-gel immunodiffusion with glycoprotein antigen. The prediction equation, based on 473 observations from 130 animals, was log10 inverse titer = 1.29 -0.012 age (days). The half-life of BLV antibodies was estimated to be 25.8 days. Ages at which colostral antibodies were last detected were between 51 and 187 days. Normal limits of antibody decay were estimated and used to identify virus-induced active antibodies in calves during the colostral antibody period. Calves known to be infected were identified between 2 and 180 days of age, using 95% limits. Application of this procedure for the early serologic detection of BLV-infected calves in eradication or control programs is discussed.     

Protection of colostral antibodies against bovine leukemia virus infection in calves on a California dairy.

A three-year prospective study involving 244 calves was undertaken on a California dairy to evaluate the protective role of colostral antibodies against bovine leukemia virus (BLV) infection in calves. Calves were followed from birth to the time they left their individual hutch (TLIH), at about 90 days of age. The probability of being infected at TLIH and the daily risk of infection between birth and TLIH were modelled using the logistic and the Cox models, respectively. Calves with no detectable antibodies during the first week of life were up to 2.00 and 2.75 times more likely to be infected at TLIH compared to calves with low and high concentrations of antibodies during the first week of life, respectively (p = 0.01). When the daily risk was modelled, calves without antibodies at the estimated day of infection were up to 3.4 and 11.6 times more likely to become infected than calves with low and high concentrations of antibodies on that day, respectively (p less than 0.001). Results indicated that calfhood infection may be reduced by about 45% through the feeding of colostrum with BLV antibodies. Further reduction in infection may be possible by feeding calves milk powder, milk replacer, and/or milk from noninfected cows. Results also indicated that quantification of the effect of a time-dependent risk factor, such as colostral antibody concentration, might be affected if treated as a fixed factor.     

Effect of colostrum administration by use of oroesophageal intubation on serum IgG concentrations in Holstein bull calves

OBJECTIVE: To determine the amount of colostral IgG required for adequate passive transfer in calves administered colostrum by use of oroesophageal intubation and evaluate the impact of other factors on passive transfer of colostral immunoglobulins in calves. ANIMALS: 120 Holstein bull calves. PROCEDURES: Calves were randomly assigned to specific treatment groups on the basis of volume of colostrum administered and age of calf at administration of colostrum. Colostrum was administered once by oroesophageal intubation. Equal numbers of calves received 1, 2, 3, or 4 L of colostrum, and equal numbers of calves received colostrum at 2, 6, 10, 14, 18, or 22 hours after birth. Serum samples were obtained from calves 48 hours after birth for IgG determination by radial immunodiffusion assay. Effects of factors affecting transfer of colostral immunoglobulins were determined by use of a stepwise multiple regression model and logistic regression models. RESULTS: A minimum of 153 g of colostral IgG was required for optimum colostral transfer of immunoglobulins when calves were fed 3L of colostrum at 2 hours after birth. Substantially larger IgG intakes were required by calves fed colostrum > 2 hours after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Feeding 100 g of colostral IgG by oroesophageal intubation was insufficient for adequate passive transfer of colostral immunoglobulins. At least 150 to 200 g of colostral IgG was required for adequate passive transfer of colostral immunoglobulins. Use of an oroesophageal tube for administration of 3 L of colostrum to calves within 2 hours after birth is recommended.     

Effects of the ingestion of whole colostrum or cell-free colostrum on the capacity of leukocytes in newborn calves to stimulate or respond in one-way mixed leukocyte cultures

OBJECTIVE: To evaluate effects of colostral cells on the ability of neonatal leukocytes to respond in a mixed leukocyte response (MLR) as a means of evaluating specific immune responsiveness. ANIMALS: 10 Holstein calves, their respective dams, and 10 unrelated adult Holstein cows. PROCEDURE: Soon after birth, their calves were fed maternal whole colostrum or colostrum after cells were removed by centrifugation. Responses for leukocytes obtained from calves during the first 5 weeks after birth, their dams, and unrelated cows were measured by use of 1-way MLR as an indicator of immune development. An internal control treatment, proliferation of lymphocytes stimulated with Staphylococcus enterotoxin B (SEB), was also measured. RESULTS: Transfer of colostral leukocytes had a significant effect on the MLR and SEB-induced response in calves. Calves receiving whole colostrum had enhanced responses to maternal and unrelated leukocytes 24 hours after ingestion of colostrum. These responses decreased quickly, indicating direct modulation of the neonatal immune response. Calves receiving whole colostrum effectively stimulated the MLR by 24 hours after ingestion of colostrum. In contrast, calves receiving acellular colostrum did not effectively stimulate the MLR until 2 to 3 weeks after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Ingestion of maternal colostral leukocytes immediately after birth stimulates development of the neonatal immune system. These maternal leukocytes enhance development of antigen-presenting capacity as indicated by their ability to stimulate the MLR and SEB response. The influence of ingested maternal cells on neonatal immunity was also indicated by a reduction in reactivity of neonatal cells to maternal alloantigens.     

Serum immunoglobulin G concentrations in calves fed fresh and frozen colostrum

OBJECTIVE: To determine whether serum IgG concentrations in neonatal calves are adversely affected by short-term frozen storage of colostrum. DESIGN: Prospective study. SAMPLE POPULATION: Experiment 1 consisted of 10 pairs of Holstein calves (n = 20) fed matched aliquots of either fresh (n = 10) or frozen and thawed (10) colostrum. In experiment 2, 26 Holstein calves were fed either fresh (n = 13) or frozen and thawed (n = 13) colostrum. PROCEDURE: Experiment 1 consisted of calves resulting from observed parturitions; calves were randomly assigned to treatment groups (fresh or frozen and thawed colostrum) in pairs. Calves were fed 4 L aliquots of colostrum via oroesophageal intubation at 3 hours of age. Serum IgG concentrations at 2 days of age were compared between the 2 groups by use of a paired t-test. Experiment 2 consisted of calves resulting from observed parturitions; calves were randomly assigned to treatment groups (fresh or frozen and thawed colostrum). Calves were fed 4 L aliquots of colostrum via oroesophageal intubation at 3 hours of age. Regression analysis was used to determine whether calf serum IgG concentration was a function of colostral IgG concentration and colostrum storage group. RESULTS: Significant differences were not observed between the 2 groups in experiment 1. No significant relationship was observed between colostrum storage group and serum IgG concentration in experiment 2. The model that best predicted serum IgG concentrations accounted for 20% of the variability in serum IgG concentration. CONCLUSION AND CLINICAL RELEVANCE: Frozen colostrum is an adequate source of IgG for calves.     

An attempt to protect calves against experimental bovine leukosis using allografts

Six calves sensitised by implanting skin from a calf were later inoculated with lymphocytes from the same calf after the calf had been infected with bovine leukosis virus (BLV). Two out of 6 calves challenged did not develop BLV antibodies and BLV was not isolated from these animals, whereas all of the 5 control calves became infected with BLV.     

A case of an embryo transfer calf infected with bovine leukemia virus from the recipient cow

A case was discovered where the embryo transfer (ET) calf had been infected with bovine leukemia virus (BLV) from the recipient cow. The embryo was transferred from the BLV-uninfected donor cow to the recipient cow. However, the BLV test had not been performed to the recipient cow before ET was performed. The ET calf was raised in a calf hatch from birth to 1-month old and was given the recipient cow's colostrum and milk artificially. The ET calf was raised with the two other calves from a 1-month old to a 6-month old. The BLV test was performed to the ET calf by agar gel precipitation (AGP) and passive haemagglutination (PHA) assay when the ET calf was 6 months old. Because the ET calf was positive, the BLV test was performed to the recipient cow, the two other calves raised with the ET calf and the two dams of the two other calves. Because the recipient cow only was positive at the time of the first test, we judged that the ET calf had been infected with BLV from the recipient cow. The importance of the BLV test being carried out on the recipient cow for the prevention of enzootic bovine leukemia in a case of ET was recognised.     

Antibody responses following administration of a Cryptosporidium parvum rCP15/60 vaccine to pregnant cattle

Cryptosporidium parvum is a zoonotic Apicomplexa-protozoan pathogen that causes gastroenteritis and diarrhea in mammals worldwide. Globally, C. parvum is ubiquitous on dairy operations and is the pathogen most commonly diagnosed in association with calf diarrhea. Here, we describe the antibody response in 20 pregnant cows to a recombinant C. parvum oocyst surface protein (rCP15/60) vaccine compared with 20 controls, and the antibody response in 19 calves fed the rCP15/60-immune colostrum from these vaccinated cows compared with 20 control calves. Cows vaccinated with rCP15/60 produced a significantly greater antibody response compared to controls (p<0.0001) and this response was strongly associated with the subsequent level of colostral antibody (r=0.82, p<0.0001). Calves fed rCP15/60-immune colostrum showed a dose-dependent absorption of antibody, also associated with colostral antibody levels (r=0.83, p<0.0001). Currently, drug therapy against cryptosporidiosis is limited making development of an effective vaccine attractive. This report describes the first stages in development of a C. parvum rCP15/60 vaccine designed to confer passive protection to calves against cryptosporidiosis.     

Bovine leukemia virus: Duration of BLV colostral antibodies in calves from commercial dairy herds

A study was conducted to determine the duration of colostral antibodies to bovine leukemia virus (BLV) in diary calves from commercial dairy farms. Sera of pregnant dams from four different dairy farms and sera of the calves of these dams were analyzed for BLV antibodies using the agar gel immunodiffusion (AGID) test. Precolostral serum samples were collected from the female calves of known BLV serologically positive dams. Postcolostral serum samples of the same calves were collected on Day 2 and biweekly until 2 consecutively negative AGID tests performed 4 weeks apart were obtained. Subsequently, the biweekly serum samples from each calf were analyzed quantitatively for BLV antibodies with the AGID test. End-point titers were determined using phosphate buffered saline to make two-fold dilutions. A logarithmic transformation of the inverse of the end-point titer was used to determine the regression line of antibody decay for each calf. Estimated weighted regression analysis was used to determine the least-squares regression line for 27 of the 38 calves sampled. The duration of colostral antibodies was calculated as 71 days using the prediction equation. The minium and maximum durations of colostral antibodies were 14 days and 147 days, respectively. The half-life of the antibodies was 36.05 days. Factors affecting the duration of BLV colostral antibodies and the practical applicability of this study were discussed.     

Eradication of bovine leukemia virus infection from a high-prevalence herd, using radioimmunoassay for identification of infected animals

Radioimmunoassay (RIA), using the virion glycoprotein antigen, was applied in an attempt to eradicate bovine leukemia virus (BLV) infection from a herd in which virtually all the adult cattle are infected. Considering that most calves born to BLV-infected cows are negative for BLV at birth and remain negative for the first several months of life, the eradication program was based on the identification and isolation of the BLV-free calves born to infected cows. Twenty-five calves raised on colostrum and milk from their infected dams were classified as BLV-free on the basis of negative results in the RIA at 6 to 8 and 9 to 11 months of age. These animals were maintained in either complete (10 calves) or partial (15 calves) isolation from infected cattle and were examined at regular intervals for BLV and BLV antibodies. With the exception of 1 calf in the group raised in partial isolation, the animals have remained free of BLV up to the time of the last evaluation, when they were 32 to 35 months old. At these ages, more than 90% of the nonisolated cattle in the herd are BLV-positive. The data also show that this eradication trial would have failed if, in the initial procedure used to classify the calves as BLV-free, the agar gel immunodiffusion test instead of the RIA had been used. Inasmuch as the 25 calves in this study were fed colostrum and milk from their dams, the fact that only 1 of the calves became infected during the 26 to 29 months of observation provides further evidence that milk-borne transmission of BLV is infrequent and perhaps inconsequential.     

Vertical transmission of bovine leukemia virus and bovine immunodeficiency virus in dairy cattle herds.

Vertical transmission of bovine leukemia virus (BLV) and bovine immunodeficiency virus (BIV) was investigated in five dairy cattle herds in Hokkaido, where 36.1 and 17.0% of cattle were BLV and BIV seropositive, respectively, and 9.9% of dams were co-infected with both BIV and BLV. Twenty six cases of offspring born from dams infected with only BLV (17 cases) or with both BIV and BLV (9 cases) were examined for the presence of BLV and BIV before and after colostrum feeding by polymerase chain reaction (PCR) and syncytium assay. After birth, all calves were separated immediately from their dams. The offspring born from BLV-positive dams were BLV-negative before colostrum feeding, suggesting that no transplacental transmission had occurred. Thereafter, these offspring were fed colostrum or milk from their dams, but still remained BLV-negative. The other offspring born from BLV-positive dams were fed with BLV-negative colostrum, or with pasteurized BLV-positive colostrum. All these calves remained negative for BLV infection, suggesting that in utero transmission of BLV is negligible. In the case of offspring born from dams co-infected with BLV and BIV, calves were BIV-positive before colostrum feeding at 1 day after the birth, indicating in utero transmission of BIV. After colostrum feeding from their dams, newborn calves became BLV-positive. In addition, one calf was BLV-positive even before colostrum feeding. These results suggest that BIV can be transmitted to offspring in utero, and that BLV can be transmitted through colostrum or milk if dams are infected with both BIV and BLV.     

Effect of different systems of colostral nutrition on the level of immunoglobulins in the blood of calves]

New-born calves, artificially fed colostrum or native colostral whey, either dried or preserved by another method, had good health and good weight gains (between 0.05 and 0.60 kg). No greater differences were observed between the groups of calves given three times the colostrum of their mothers, calves given mixed colostrum, and calves fed colostral whey powder. In all groups only individual differences in IgG content in the blood serum were observed after 48 hours from birth. Hypogammaglobulinaemia occurred in individual cases both in calves given small amounts of colostrum or colostral whey and in calves given sufficient quantities. The time that had elapsed from birth to the first drinking did not exert any greater influence upon the IgG level in the blood; the decisive factor was the amount of colostrum taken in by the calf in the first dose. The rate of the absorption of IgG1, IgG2, IgA, and IgM from colostrum and the concentration of the immunoglobulins in the serum depended on the quantity of colostrum in the first dose and were not influenced to any greater degree by the amount of colostrum given to the calves in further doses. The amount of IgG in the blood serum of calves corresponded approximately to the level of colostral antibodies to the virus PI-3. The antibodies to the virus PI-3 and small quantities of IgG were observed also in the serum to new-born calves before drinking colostrum.     

Effect of oral inoculation of Escherichia coli on colostral antibody production in cattle.

Oral inoculation of approximately 1.2 x 10(9) viable Escherichia coli to pregnant cows resulted in increased blood serum and colostral whey titers to the "O" antigen. The antibody titers were more pronounced in colostral whey and were correlated with the inoculum strain of Escherichia coli. There was no correlation between antibody titers of the colostrum ingested and the resulting serum antibody titers of the calves. The incidence of diarrhea in calves did not correlate with the antibody titer in the colostrum. The occurrence of diarrhea was significantly greater in calves that did not ingest colostrum until they were 12 hours old, compared with calves that had free access to their dams and suckled within an hour of birth.     

Timing of seroconversion and acquisition of positive polymerase chain reaction assay results in calves experimentally infected with bovine leukemia virus

OBJECTIVE: To determine the interval to provirus and serum antibody detection (via PCR assay and ELISA, respectively) in calves after experimental inoculation with bovine leukemia virus (BLV). ANIMALS: 8 colostrum-deprived, BLV-negative Holstein bull calves (> or = 6 weeks old). PROCEDURES: Via IM injection, each calf received a fresh whole-blood inoculum (day 0) calculated to contain 2 x 10(6) lymphocytes. Blood samples for the ELISA and PCR assay were collected from calves immediately prior to inoculation and weekly thereafter for 7 weeks. Mean and median number of weeks to PCR-detected conversion of BLV status and seroconversion were calculated. Point sensitivity and cumulative sensitivity of the 2 assays were calculated at each sample collection. At each sampling time, the proportion of calves identified as infected by the cumulative weekly ELISA and PCR assay results was compared by use of a Fisher exact test. RESULTS: In 5 calves, conversion of BLV status was detected via PCR assay before seroconversion was identified. However, seroconversion preceded PCR-detected conversion in 2 calves. In 1 calf, both assays yielded positive results at the same test date. These differences were not significant. CONCLUSIONS AND CLINICAL RELEVANCE: In experimentally inoculated BLV-negative calves, conversion of BLV status was detected via PCR assay more quickly than via ELISA; this difference was not significant and probably not clinically important. The PCR assay may be useful as a confirmatory test in animals of exceptional value; tests based on viral identification may become critically important if vaccines against BLV infection are developed and marketed.     

Comparison of three methods of feeding colostrum to dairy calves

Absorption of colostral immunoglobulins by Holstein calves was studied in 3 herds in which 3 methods of colostrum feeding were used. Failure of passive transfer, as determined by calf serum immunoglobulin G1 (IgG1) concentration less than 10 mg/ml at 48 hours of age, was diagnosed in 61.4% of calves from a dairy in which calves were nursed by their dams, 19.3% of calves from a dairy using nipple-bottle feeding, and 10.8% of calves from a dairy using tube feeding. The management factor determined to have the greatest influence on the probability of failure of passive transfer in the herds using artificial methods of colostrum feeding (bottle feeding or tube feeding) was the volume of colostrum fed as it affected the amount of IgG1 received by the calf. In dairies that used artificial feeding methods, failure of passive transfer was infrequent in calves fed greater than or equal to 100 g IgG1 in the first colostrum feeding. In the dairy that allowed calves to suckle, prevalence of failure of passive transfer was greater than 50% even among calves nursed by cows with above-average colostral IgG1 concentration. Analysis of the effect of other management factors on calf immunoglobulin absorption revealed small negative effects associated with the use of previously frozen colostrum and the use of colostrum from cows with long nonlactating intervals.     

The influence of colostral leukocytes on the immune system of the neonatal calf. I. Effects on lymphocyte responses

The influence of colostral leukocytes on lymphocyte counts in the blood of calves and on lymphocyte responses, in particular the Concanavalin A-induced blastogenic response in vitro and the formation of antibodies against sheep erythrocytes, was investigated for four weeks postnatum using four experimental groups. The calves received either complete colostrum (COL+, n = 16), cell-depleted colostrum (COL-, n = 16), colostral cell-supplemented milk substitute (MS+, n = 7) or pure milk substitute (MS-, n = 6) during their first three days of life. In contrast to the calves fed with cell-depleted colostrum (COL-) the calves fed with complete colostrum (COL+) showed no decrease of lymphocyte numbers in the blood on the second day of life, uniform blastogenic responses to two different Concanavalin A concentrations, slightly enhanced antibody formation against sheep erythrocytes and a high spontaneous proliferation of mononuclear cells during the first week of life. In the calves fed with milk-substitute supplemented with colostral cells (MS+) a higher blastogenic response to Concanavalin A and an intensified formation of antibodies against sheep erythrocytes was observed as compared to the MS- calves. A passage of vital colostral lymphocytes through the intestinal wall is postulated. They seem to stimulate and regulate the blastogenic response and enhance the T-helper cell-dependent formation of antibodies against sheep erythrocytes in calves.     

Transfer of maternal colostral leukocytes promotes development of the neonatal immune system Part II. Effects on neonatal lymphocytes

It has been established that maternal leukocytes, conditioned by the mammary environment, cross the neonatal gut and circulate in the newborn calf. However, the impact of these cells on the development of neonatal immunity remains to be determined. This study examined the effects of maternal colostral leukocytes on development and maturation of neonatal adaptive immunity by examining the expression of surface markers on neonatal lymphocytes. At birth, neonatal calves were fed whole colostrum, or colostrum that had the maternal cells removed (cell-free colostrum), from their respective dams. Peripheral blood samples were collected at regular intervals over the first 4 weeks of life and lymphocytes were evaluated for surface expression of cellular markers. The results of these studies demonstrated that calves receiving whole colostrum had fewer CD11a positive lymphocytes in circulation during the first 2 weeks of life and this marker was expressed at a lower density than calves receiving cell-free colostrum. In addition, calves receiving whole colostrum also had a higher percentage of lymphocytes expressing the activation markers CD25 and CD26 by 7 days after birth. During the first week of life, lymphocytes from calves receiving whole colostrum had a higher density of MHC class I expression on their surfaces than cells from calves receiving cell-free colostrum. In general, these results indicate that transfer of maternal cells with colostrum allows for more rapid development of lymphocytes and maternal cells appeared to enhance their activation.     

A Reevaluation of Routine Force-feeding of Dam's Colostrum to Normal Newborn Beef Calves

Forty-seven beef calves born to a group of second-calf Hereford and Hereford x Angus cows were used to assess the practical value of force-feeding dam's colostrum. The first 40 calves born were assigned alternately to two equal groups (I and II). One group was force-fed up to I L of dam's colostrum per calf. All these animals were bled at 0 and 48 h after birth. A further group (III) of seven calves born were not handled until they were bled at 48 h. A variety of methods were used to estimate immunoglobulin levels in colostral whey and serum samples. In evaluating the efficiency of passive humoral antibody transfer from dam to offspring, no significant differences were evident except in radial immunodiffusion levels which were increased in group III. The percentages of calves sucking within one hour of birth were 30%, 15% and 100% for groups I, II and III, respectively. Under the conditions of this study it appears that force-feeding of dam's colostrum to the newborn beef calf is disruptive and does not confer any practical benefit on such calves in terms of passive humoral antibody transfer.     

Transplacental and oral transmission of wild-type bluetongue virus serotype 8 in cattle after experimental infection

Potential vertical transmission of wild-type bluetongue virus serotype 8 (BTV-8) in cattle was explored in this experiment. We demonstrated transplacental transmission of wild-type BTV-8 in one calf and oral infection with BTV-8 in another calf. Following the experimental BTV-8 infection of seven out of fifteen multi-parous cows eight months in gestation, each newborn calf was tested prior to colostrum intake for transplacental transmission of BTV by RRT-PCR. If transplacental transmission was not established the calves were fed colostrum from infected dams or colostrum from non-infected dams spiked with BTV-8 containing blood. One calf from an infected dam was born RRT-PCR positive and BTV-specific antibody (Abs) negative, BTV was isolated from its blood. It was born with clinical signs resembling bluetongue and lived for two days. Its post-mortem tissue suspensions were RRT-PCR positive. Of the seven calves fed colostrum from infected dams, none became infected. Of the six calves fed colostrum from non-infected dams spiked with infected blood, one calf became PCR-positive at day 8 post-partum (dpp), seroconverted 27 days later, and remained RRT-PCR and Abs positive for the duration of the experiment (i.e., 70 dpp). This work demonstrates that transplacental transmission in late gestation and oral infection of the neonate with wild-type BTV-8 is possible in cattle under experimental conditions.